Total or near-total occlusions in arteries can prevent all or nearly all of the blood flow through the affected arteries. It has been estimated that 5% to 15% of patients on whom percutaneous coronary angioplasty (PTCA) is attempted are found to have chronic total occlusions (CTO""s) of at least one coronary artery. Chevalier, B. et al., Chronic Total Occlusion, The Paris Course on Revascularization, Pages 131-148 (May 2000). In patients who suffer from coronary CTO""s, the successful performance of a PTCA is a technical challenge. The factor that is most determinative of whether the interventionalist can successfully perform PTCA on patient who presents with a coronary CTO is the interventionalist""s ability (or inability) to advance a suitable guidewire from a position within the lumen of the artery upstream of the lesion, across the lesion (i.e., either through the lesion or around it), and then back into the artery lumen at a location downstream of the lesion.
In some instances, such as where the occlusive matter is soft or where the occlusion is less than total, the guidewire can simply be pushed through the occlusive matter itself, thereby allowing the guidewire to remain within the artery lumen. However, in other cases, such as where the artery is totally occluded by hard, calcified atherosclerotic plaque, the guidewire may tend to deviate to one side and penetrate through the intima of the artery, thereby creating a neo-lumen through the sub-intimal space (i.e., within the wall of the artery between the intima and adventitia). In these cases, after the distal end of the guidewire has been advanced to a position distal to the lesion, it is then necessary to divert or steer the guidewire from the sub-intimal space back into the lumen of the artery at a location downstream of the lesion. This process of causing the guidewire to reenter the artery lumen is often difficult and others have proposed various means for dealing with such problem. For example, PCT International Publication No. WO 00/18323 describe techniques where a catheter that has a through lumen terminating distally in a laterally directed outlet port is advanced into the sub-intimal space past the lesion and a penetrator or guidewire is then advanced through the catheter, out of the laterally directed outlet port, and back into the lumen of the artery. WO 00/18323 further states that optionally a wire may be passed through a lumen of the catheter and that such wire may further comprise an imaging apparatus such as an ultrasonic imaging means. Also, WO 00/18323 states that the catheter may include a marker near its distal end that is visible on fluoroscopy and that such marker may be configured to permit visual determination of the rotational orientation of the distal end of the catheter when viewed as a two-dimensional fluoroscopic image. However WO 00/18323 does not describe any means for correlating the rotational orientation of the catheter to the trajectory on which the penetrator or guidewire will subsequently advance. A number of variable can affect the trajectory on which the penetrator or guidewire will advance, including the location of the outlet aperture from which the penetrator or guidewire exits the catheter body, the density and resistance of the tissue through which the penetrator or guidewire advances and any bias, shape or curvature that the penetrator or guidewire will assume after it is no longer constrained by the catheter.
Another approach to bypassing a CTO, as described in U.S. Pat. No. 6,068,638 (Makower), U.S. Pat. No. 5,830,222 (Makower) and U.S. Pat. No. 6,190,353B1 (Makower, et al.) utilizes a tissue penetrating catheter device that has an on board guidance element that allows a tubular penetrator cannula to penetrate outwardly through the intima of the artery wall upstream of the lesion after which a member is advanced trough the cannula and bores through tissue located outside of the vessel""s intima, to a position distal to the obstructive lesion, and then reenters the lumen of the artery at a location downstream of the lesion. Tissue penetrating catheters of this type, having on-board guidance and/or orientation capabilities and penetrator cannulas that are advanceable laterally from the catheter body, have previously been devised. (Transaccess(copyright) catheters by Transvascular,(copyright) Inc., Menlo Park, Cailf.).
There exists a need in the art for the development of new and better techniques for catheter-based treatment of CTO and other total or near-total obstruction of arteries or other anatomical conduits, especially with respect to improving the available techniques for causing a guidewire to reenter the lumen of an artery from a location within the sub-intimal space or even outside of the artery wall and for facilitating verification of the intended re-entry into the artery lumen and prompt delivery of arterial blood or some other oxygenated perfusate to tissues that would normally receive arterial bloodflow from the obstructed artery.
The present invention provides methods for bypassing total or near total occlusions of arteries or other anatomical conduits through the use of catheters that include a) penetrators that are advanceable from the catheter, such penetrators having lumens that extend therethrough such that a guidewire can be advanced through the penetrator, blood or marker fluid can be withdrawn through the penetrator lumen to verify that the distal end of the penetrator is in fact positioned in the artery lumen and/or substance(s) such as radiographic contrast medium, therapeutic or diagnostic agents or oxygenated perfusate may be injected through the lumen of the penetrator and b) one or more orientation element(s) (e.g., marking(s), imaging apparatus, sensor(s), emitter(s) and/or combinations thereof) that are useable to determine the rotational orientation of the catheter within the body relative to the trajectory on which the penetrator will subsequently advance thereby enabling operator to precisely position and orient the catheter before advancement of the penetrator such that the penetrator will accurately reenter the lumen of the artery or other conduit from a location within or outside of the wall of the artery or other conduit.
In accordance with one embodiment of the invention, there is provided a method for bypassing an obstruction in an artery or other anatomical conduit by first advancing a first elongate member (e.g., a cardiovascular guidewire) into the lumen of the obstructed artery or body conduit to a position where its distal end is proximal to the obstruction. Thereafter, using techniques known in the prior art, the operator maneuvers the first elongate member within or outside of the wall of the artery or other luminal anatomical structure and past the obstruction position where the distal end of the first elongate member is distal to the obstruction and outside of the lumen of the anatomical conduit. Thereafter, a penetrating catheter that comprises i) an elongate, flexible catheter body having a distal end, ii) a lumen extending longitudinally through at least a distal portion of the catheter body to permit the catheter device to be advanced over an elongate member iii) a penetration member or penetrator that penetrates into or through the wall of the anatomical conduit in which the catheter body is positioned and iv) an orientation element useable to enable the operator to determine the rotational orientation of the catheter body within the anatomical conduit so that the penetration member may be aimed at a target location, is advanced over the first elongate member to a position where the distal end of the catheter body is positioned outside of the lumen of the anatomical conduit, distal to the obstruction. Thereafter, the catheter body is rotationally oriented with the aid of the orientation element such that, when the penetration member is subsequently advanced from the catheter body, the penetration member will enter the lumen of the anatomical conduit distal to the obstruction. After the catheter has been placed in such rotational orientation, the penetration member is advanced into the lumen of the anatomical conduit. A second elongate member (e.g., a cardiovascular guidewire) may then be passed through the lumen of the penetration member and into the lumen of the anatomical conduit. Thereafter, the penetration member is retracted into the catheter and the catheter is removed, leaving the second elongate member in place. The obstruction is thereby crossed. The tract formed around the obstruction may then be enlarged and/or stented in accordance with well known techniques to allow flow (e.g., blood flow) around the obstruction.
In accordance with another embodiment of the invention, there is provided another method for bypassing an obstruction in an artery or other anatomical conduit. In this embodiment of the method, a first elongate member (e.g., a cardiovascular guidewire) is initially advanced into the anatomical conduit proximal to the obstruction. Thereafter, a penetrating catheter that comprises i) an elongate, flexible catheter body having a distal end, ii) a lumen extending longitudinally through at least a distal portion of the catheter body to permit the catheter device to be advanced over an elongate member iii) a penetration member or penetrator that penetrates into or through the wall of the anatomical conduit in which the catheter body is positioned and iv)an orientation element useable to enable the operator to determine the rotational orientation of the catheter body within the anatomical conduit so that the penetration member may be aimed at a target location, is advanced over the first elongate member to a position where the distal end of the catheter body is positioned within the lumen of the anatomical conduit proximal to the obstruction. If desired, the orientation element may optionally be used at this time to rotationally orient the catheter within the lumen of the anatomical conduit. Thereafter, the penetration member is advanced from the catheter and into or through the wall of the anatomical conduit. A second elongate member (e.g., a second cardiovascular guidewire) is then advanced through the penetrator, out of the distal end of the penetrator and through tissue located within or outside of the wall of the anatomical conduit, to a position where the distal end of the second elongate member is distal to the obstruction but still outside of the lumen of the anatomical conduit. The penetrator is retracted into the catheter and the catheter is then removed, leaving the second elongate member in place. The penetrating catheter is then reinserted and advanced over the second elongate member to a position where the distal end of the catheter device is distal to the obstruction and outside of the lumen of the anatomical conduit. The orientation element is then used to rotationally orient the catheter such that, when the penetration member is subsequently advanced from the catheter body, the penetration member will enter the lumen of the anatomical conduit distal to the obstruction. Thereafter, the penetration member is advanced from the catheter and into the lumen of the anatomical conduit, downstream of the obstruction. A third elongate member (e.g., a cardiovascular guidewire) may then be passed through the lumen of the penetration member and into the lumen of the anatomical conduit. Thereafter, the penetration member is retracted into the catheter and the catheter is removed, leaving the third elongate member in place. The obstruction is thereby crossed. The tract formed around the obstruction may then be enlarged and/or stented in accordance with well known techniques to allow flow (e.g., blood flow) around the obstruction.
In cases where the anatomical conduit is an obstructed artery, the bypass tract will be formed outside of the intima of the artery. Sometimes, the bypass tract will be entirely within the artery wall. Other times, the bypass tract may penetrate outside of the artery wall into tissue or space adjacent to the artery.